The objective of this research is an understanding of the lipid-protein interactions through the study of three protein systems: phosopholipase A2, melittin, and a sterol carrier protein. Studies on phospholipase A2 include the isolation of a membrane-bound enzyme from sheep erythrocytes and its characterization in lipid monolayer assay systems. Studies with melittin involve mainly interactions of the peptide with lipid monolayer systems. Studies of interactions of a sterol carrier protein with micellar and liposomal lipid systems involve fluorescence and gel filtration techniques.